Why does copy rotation constraint invert after 180 degrees
Maybe you can alternatively do it with drivers instead.

Rather than add constrains use a driver on the rotation properties of the hour hand by right clicking them and choosing Add Driver &gt; Manually Create Later

Then proceed to the Graph Editor, change to Drivers from the header, and choose the desired channel (Z in this case).
From there open the Properties Panel (N Key), Drivers tab choose the option Scripted Expression and add a new variable.
Use the Transform Chanel option, pick the other hand and choose its $Z$ Rotation. The scripted expression should read something along the lines of $var/12$ so it rotates at one twelfth of the angular speed.